Interior keeps fogging up! Options

[block]

Mornings/afternoons are fine because there's no moisture built up but once it hits teens to single digit temps my windows would fog the hell up. I've cleaned it with so many different solutions that I've run out of ideas. Turning up the heat doesn't help, same with cooling it. It'll keep building up and im getting sick of driving with fog smears and not seeing at night. I have to wipe every 5 minutes or so lol. I do have a 24 inch crack across my windshield but that should affect be wise I've driven cars with cracked windshield and its been fine. Heater core is good since its blowing hot heat....going to change coolant and see if that helps. Anyone have any other ideas or experiences that may help solve the issue? Sorry it may not make any sense because im just rambling things out from my phones. Thanks!

[RabidTRD]

Make sure the AC is ON when you're trying to defrost. Otherwise you're just blowing moist hot air and it won't clear anything. Common places for moisture leaks: rear fender wells rot out and it gets in there, buildup in the body drains from clogged drain plugs.